Polycarbonate resins exhibit excellent transparency and high impact resistance and are widely utilized as electric or electronic parts and mechanical parts of appliances. In recent years, polycarbonate resins have contributed to creation of new materials called polymer blends or polymer alloys in combination with other resins.
Conventional polycarbonate resins for these uses have an elongation of about 100% in a tensile test though exhibiting plastic hardness. In order to obtain modified polycarbonate resins with further increased elongation, various improvements have been added to a process comprising copolymerization of an aromatic compound having crystallinity and an aliphatic compound having rubbery properties.
For example, processes for producing soft polycarbonate resins from bisphenol A or a bisphenol A block and polytetramethylene ether glycol were proposed as described in Journal of Applied Polymer Science, pp. 343-352 (1961) and Journal of Polymer Science, Part C, pp. 707-730 (1963). In connection to the similar reaction mode, reactivity of various aliphatic glycol compounds is studied in JP-A-49-133494 and JP-A-51-61597 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), and modified polycarbonate resins prepared by using polyethylene glycol or polytetramethylene ether glycol as an aliphatic compound are described in JP-A-56-36517, JP-A-60-94420, JP-A-62-11724, JP-A62-161825, and U.S. Pat. No. 3,287,442.
While these known modified polycarbonate resins have an increased tensile elongation as a mechanical property as compared with general polycarbonate resins, they have reduced strength only to provide moldings of low strength.
Further, polycarbonate resins are frequently used as a modifier for improving impact resistance of other resins. Polycarbonate resins for such use are also required to have well-balanced mechanical strength and elongation.
The conventional soft polycarbonate resin obtained from bisphenol A and polytetramethylene ether glycol has poor mechanical properties at low temperatures due to its high glass transition temperature. Therefore, it is unsuitable for use in a low temperature environment, for example, as a constructive material.